The values of radius, latitude, and longitude are not important, but they are being defined when the script executes. What bothers me is that the snippet of code above returns no results; essentially meaning that the way that the query is being executed is wonky. I executed the SQL query (including the set variables with actual values, and it returned the correct number of results).

If I modify the query to just be a simple SELECT FROM query (SELECT * FROM poi_table) it returns results. What is going on here?